ajax的簡單封裝

//--------------------------------------------------------------------------------------

//封裝XMLHTTP的Request類的代碼
var $ajax = new Object();
function getAjax() {
    var ajax = false;
    try {
        ajax = new ActiveXObject("Msxml2.XMLHTTP");
    }
    catch (e) {
        try {
            ajax = new ActiveXObject("Microsoft.XMLHTTP");
        }
        catch (E) {
            ajax = false;
        }
    }
    if (!ajax && typeof XMLHttpRequest != 'undefined') {
        ajax = new XMLHttpRequest();
    }
    return ajax;
}
//封裝XMLHTTP向伺服器發送請求的操作
$ajax.send = function (url, method, callback, data) {
    var req = getAjax();  //得到一個XMLHTTP的執行個體
    //當XMLHTTP的請求狀態發生改變時調用
    req.onreadystatechange = function () {
        // 當請求已經載入
        if (req.readyState == 4) {
            // 當請求返回成功
            if (req.status == 200) {
                // 當定義了成功回呼函數時，執行成功回呼函數
                if (callback)
                    callback(req, data);
            }
            // 當請求返回錯誤
            else {
                alert("當載入資料時發生錯誤 :\n" + req.status + "/" + req.statusText);
            }
            try {
                delete req;
                req = null;
            } catch (e) { }
        }
    }
    //如果以POST方式回傳伺服器
    if (method == "POST") {
        req.open("POST", url, true);
        req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
        req.send(data);
    }
    //以GET方式請求
    else {
        req.open("GET", url, true);
        req.send(null);
    }
}

//進一步封裝XMLHTTP以POST方式發送請求時的代碼
$ajax.sendPOST = function (url, data, callback) {
    $ajax.send(url, "POST", callback, data);
}
//進一步封裝XMLHTTP以GET方式發送請求時的代碼
$ajax.sendGET = function (url, callback, args) {
    return $ajax.send(url, "GET", callback, args);
}

//--------------------------------------------------------------------------------------

以上代碼很容易但是完成了ajax的基本需求用法也很簡單:

 $ajax.sendPOST("Handler.ashx", "action=reply&" + parameter,

　　function (req, data) {
                    var rel=req.responseText;

　　}

 );